1. Field of the Invention
The present invention relates in general to a light bulb of the cathode glow type which is filled with an inert gas. In particular, the invention relates to such a light bulb which includes a pair of electrodes coated with an electron-emissive material and which includes an electrically inert element which is coated with a fluorescent material.
2. Description of Prior Developments
Luminescent light bulbs have been available in numerous forms for many years. Such bulbs may include a glass envelope within which an inert gas such as argon, neon and or helium is sealed under pressure. A pair of electrodes may be energized within the glass envelope with sufficiently high voltage to ionize the gas surrounding the negative electrode or cathode so that the gas emits a visible glow. With alternating current, each electrode acts alternately as a cathode so that each electrode appears to glow constantly.
As seen in U.S. Pat. No. 2,298,581, a lining of photoluminescent material may be provided on the inner surface of the glass envelope of a light bulb so that the radiation surrounding the electrodes activates the photoluminescent material thereby increasing the intensity of illumination. Instead of coating the inner walls of the glass envelope, Sereno, in U.S. Pat. No. 2,520,513 coats or stencils letters or symbols upon a glass plate which is mounted within a glass envelope. The letters or symbols are formed of a fluorescent material which is activated by ionized gases sealed within the glass envelope.
Many other variations of negative or cathode glow light bulbs have been developed over the years for many varied applications. However, a need continually exists for such bulbs which produce new and different lighting effects. This is particularly the case in the field of special effect lighting such as used in advertising and novelty applications.